Device for squeezing flowable material out of a tubular bag

ABSTRACT

The inventive device for squeezing flowable material includes a tubular bag containing the material, as well as an injection device . The tubular bag is inserted into a cylindrical chamber of the ejection device. Its open end is located inside an outflow opening of said device. The tubular bag is clamped to the fore-part with a sealing washer, the clamping member of which cooperates exclusively with the outflow opening edge formed by the fore-part.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is the national stage of International Application No.PCT/EP97/04338 filed Aug. 8, 1997.

BACKGROUND OF THE INVENTION

It is known to squeeze a free-flowing, pasty mass, such as a sealingcompound or dental impression mass, out of a tubular bag by the latterbeing put into a cylinder space which is acted upon from one end by apiston and has a discharge opening or delivery nozzle at the other end,at which the bag is open. In this case, it is particularly importantthat that end of the tubular bag which contains the bag opening issealed off from that end of the cylinder space and of the deliverynozzle which forms the discharge opening. If, for this purpose, thetubular bag is firmly connected to the device forming the cylinder space(FR-A 1 161 905), repeated use of the squeezing-out device for aplurality of tubular bags is made impossible. If the tubular bag isconnected to the delivery nozzle in one piece or via thread (DE-A 35 00625), the exchange of the tubular bag is prevented or made moredifficult, provided the nozzle is also not designed as a throw-awaypart. The latter is often not possible or is undesirable. Thearrangement of sealing elements between the end of the tubular bag andthe delivery nozzle or discharge opening (EP-A 319 666), which sealingelements are to be fixed by special clamping or screw parts, also makesexchange difficult. To avoid these disadvantages, the arrangementmentioned in the preamble of claim 1 for squeezing out interchangeabletubular bags has been disclosed (EP-A 541 972), in which the gathered-upend, forming the bag opening, of the tubular bag is firmly connected toa sealing ring, which has a conical sealing surface, which interactswith a correspondingly conical sealing surface in the discharge openingof the squeezing-out device. Under the action of the squeezing-outpiston, the cone of the sealing ring is pressed into the conicaldischarge opening, provided it is adequately centred beforehand. In theevent of inadequate centring, sealing is not achieved. If the cone ofthe sealing ring sits in an exactly centred manner in the dischargeopening, it appears possible to achieve an adequate sealing effect aslong as the effect of the piston force continues. However, this sealingeffect ceases when the arrangement “breathes” if the piston forceceases. Since, during the squeezing-out, most of the pressure drop doesnot take place in the bag opening or the discharge opening of thesqueezing-out device but in the downstream spaces of the nozzle and themixing device which is possibly present, a considerable pressure, whichleads to corresponding extension of the associated walls, builds upduring the squeezing-out in these spaces downstream of the dischargeopening. If the squeezing-out force of the piston ceases, this extensionleads to a back pressure and a backflow of the mass in the region of thedischarge opening. As a result, the cone of the sealing ring may belifted from its conical seat in the discharge opening; the sealing gapopens and the mass can penetrate into the space, to be sealed off,between the sealing ring and the tubular bag on the one hand and thecylinder space on the other hand. The mutual centring may also be lost,so that the cone of the sealing ring is not returned into the correctseat when pressure is next applied. Contamination of the device cannottherefore be completely avoided by the known arrangement. In addition,there is the disadvantage that the discharge opening has to be carefullycleaned when the tubular bag is changed, since otherwise possiblyconsolidated residues of the mass which remain there make completesealing impossible even during the effect of the squeezing-out force, afactor which then leads to further contamination of the device. Theknown type of sealing also requires careful production and assembly ofthe parts which are involved in the sealing, and this is expensive. Itis known (EP-A-663348) to counteract these disadvantages by the ringwhich bears the cone having a rim diameter which exceeds the insidediameter of the cylinder space accommodating the tubular bag and by saidring being fixed in a circumferential groove, which is formed betweenthe end of the wall of the cylinder space and a lid forming the deliverynozzle. However, this has the disadvantage that the tubular bag can onlybe used in such devices whose cylinder space contains saidcircumferential groove and has a lid on the delivery side, the lidhaving to be opened in order to insert the tubular bag.

SUMMARY OF THE INVENTION

The object of the invention is to provide an arrangement for squeezing afree-flowing substance out of an elongated tubular bag which is lessexpensive, permits easy exchange of the tubular bag, and nonethelessensures adequate sealing.

The effect of the sealing elements of the sealing ring solely on the endface surrounding the discharge opening or on that edge of the dischargeopening which is formed by this end face makes careful cleaning of thedischarge opening, to which access is more difficult, unnecessary.Cleaning of the end face is also frequently unnecessary, sinceexperience shows that the mass rarely penetrates so far. In the regionof the edge, any residues of the mass are displaced without impairingthe sealing effect. The interacting sealing surfaces impose a smallerrequirement for accurate production and assembly, since it is notnecessary to exactly match any diameters to one another. Finally, theinvention has the advantage that the sealing is independent of therespective design of the discharge opening, and the tubular bags cantherefore be used in different squeezing-out devices. The sealing effectalso cannot be impaired by any inclination of the sealing ring.

In general, the end face surrounding the discharge opening of thesqueezing-out device is flat. It is then advisable to also design thesealing ring (apart from projecting sealing elements) to be flat, sothat it can extend parallel to the end face. This especially applieswhen, according to a further feature of the invention, it has an outsidediameter approximately equal to the diameter of the cylinder space. As aresult, effective guidance and centring of the tubular bag end isobtained during insertion into the delivery opening. Furthermore, it isadvantageous if the rim of the sealing ring has a considerable height,which prevents the canting of the sealing ring when the tubular bag isbeing inserted into the cylinder space from its rear side remote fromthe delivery side. This height is preferably at least 4 mm or 6% (better10%) of the diameter. Furthermore, it may be expedient if thecircumferential surface is entirely or partly conical or bevelled orrounded off at one or both edges in order to facilitate the insertioninto the cylinder space and if need be to also avoid the canting.

In order to avoid the lifting of the sealing elements from the end faceof the cylinder space, the sealing ring, according to a further featureof the invention, may be provided with a retaining part arresting it inthe sealing position. The invention prefers two embodiments of thisidea. The first is distinguished by the fact that the retaining part isdesigned as a clamp interacting with the inner wall of the cylinderspace. This is preferably achieved by the disc which forms or retainsthe sealing ring being flexible and by its outside diameter beingslightly larger than the inside diameter of the cylinder space. If thedisc is pushed against the end face during the squeezing-out activity ofthe piston, its outer rim, which bears under deformation against theinner surface of the cylinder space, bends slightly rearwards, the anglebetween this rim and the normal to the cylinder wall being so small inlongitudinal section that self-locking takes place. This means that thedisc is secured in the position which it thus attains. It cannot giveway if the piston force ceases, and the sealing elements remain pressedagainst the end face under the elastic force of the disc deformation. Inthis way, the breathing is prevented. In the second embodiment of theretaining part, the disc is provided with a suction holder which holdsit in place on the end face. This may involve one or more suction cups.

According to a further feature of the invention, a brake element, whichsecures the bag in the respective position in the cylinder space, isarranged on the rear end of the tubular bag. By friction, it alsoprevents the bag from slipping rearwards or even falling out of thecylinder upon withdrawal and when the cylinder is placed in the verticalposition with the outlet opening at the top. Owing to the fact that thedraw-in force, when the bag is being pushed into the cylinder space, isexerted directly on the brake element arranged on the rear tubular bagend, it need not be transmitted to the brake element via the bag and itscontents and therefore does not have an effect on the internal pressureof the bag.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is explained in more detail below with reference to thedrawing, which illustrates advantageous exemplary embodiments and inwhich:

FIG. 1 shows a schematic longitudinal section through a cartridgecontaining the tubular bag,

FIGS. 2 to 4 show partial sections through the base region of thecartridge with different sealing rings,

FIGS. 5 and 6 show longitudinal sections through a further embodiment intwo different functional positions, and

FIG. 7 shows a brake disc at the rear end of the tubular bag.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 shows the tubular bag 1 inside a so-called cartridge 2, whichcomprises a wall 3 and a base 4. Its inside diameter is dimensioned tosuit the tubular bag 1. Cartridges of this type with tubular bags areused as interchangeable inserts in devices for delivering plasticmasses, for example in devices for delivering dental multi-componentimpression masses (EP-A 492 413).

The cartridges are inserted into the device in such a way that a piston5 specific to the device can penetrate in the direction of the arrowinto the open end 6, remote from the base, of the cartridge in order tosqueeze out the tubular bag 1. The gathered-up end 7, which is closed inthe storage state, of the bag at the other end is cut off in such a waythat a bag opening 8 forms, and this bag opening 8 opens into adischarge opening 9 located in the base 4 of the cartridge. A sealingring 13 is inserted between that end face 11 of the base 4 which facesthe cylinder space 10 of the cartridge and the shoulder surface 12 ofthe tubular bag 1. When the piston 5 compresses the tubular bag 1, themass contained therein can flow through the bag opening 8 and thedischarge opening 9 into the downstream spaces (not shown) of the devicein order to be mixed, for example, with another component and finallydelivered in the desired manner. The pressure produced in the tubularbag 1 by the piston also acts via the shoulder surface 12 on the sealingring 13, so that the latter, at least during the squeezing-outoperation, forms an effective seal between the end face 11 and theshoulder surface 12. In addition, the gathered-up portion 7 is pressedagainst the wall surface of the discharge opening 9, so that an upstreamseal is obtained at this point. The term cylinder space is not intendedto imply that the wall 3 has to be cylindrical; however, it isexpediently cylindrical.

It is assumed in FIG. 1 that the base 4 of the cartridge is firmlyconnected to its wall 3 and the tubular bag 1 is inserted into thecartridge from the side remote from the delivery side. However,embodiments in which the base can be released from the wall 3 like a lidin order to insert the tubular bag 1 are also possible.

In the embodiment of the sealing ring shown in FIG. 2, this sealing ringis designed as an annular disc 14. It may be adhesively bonded to theshoulder surface 12 of the tubular bag 1. Its outside diameter is notmuch smaller than that of the cylinder space 10. It can therefore serveto centre the bag opening relative to the discharge opening when thetubular bag is inserted into the cartridge. It is made of rigid plasticin order to be able to perform this task. It also expediently has such ahigh strength that it can ensure that the annular disc 14 is in anapproximately flat position or a position parallel to the end face 11.

Close to the inner rim of the annular disc 14, an O-ring 15 (there mayalso be a plurality of O-rings) is connected in a leakproof andpreferably firm manner to the annular disc 14 by virtue of the fact thatsaid O-ring 15 is adhesively bonded in place or is clamped in place inan annular groove, for example. It is made of soft rubber or foam rubberwith a closed surface and therefore bears without gaps against the endface 11 under the pressure acting during the squeezing-out operation andthus forms effective protection against the penetration of mass from thedischarge opening 9 if mass should pass through between the gathered-upportion 7 and the wall of the discharge opening 9. The O-ring 15 ismoved so close up to the discharge opening 9 that it interacts with theedge of the latter, as a result of which the sealing effect is improved.

Since the bag opening 8 can have a larger inside diameter than knowntubular bags due to the absence of an annular part penetrating into thedischarge opening 9, its flow resistance is low, so that the degree of“breathing” and thus the risk of the ingress of the mass between thegathered-up portion 7 of the tubular bag and the wall of the dischargeopening 9 are less than in the case of known arrangements. The annulardisc 14, as shown in FIG. 4, may be provided with a raised rim 27.

If the deformed bag 1 is inserted into the cylinder 3 in a carelessmanner, the end face of the bag may be skewed slightly. Thecorresponding inclination of the end face is transmitted to the sealingring if the latter is designed as a disc or is connected to a disc whichis adhesively bonded over the full area to the end face of the bag. Thetightness may suffer from this in the embodiment according to FIG. 2 butnot in the embodiments according to FIGS. 3 and 4.

FIG. 3 shows that the sealing ring, designated overall by the referencenumeral 13, consists of a disc 16 having a circumferential surface 28,and an elastomeric O-ring 15, which is secured in a groove of the disc16 and interacts in a sealing manner with the end face 11 of thecartridge base 4. The disc 16 is connected to the end face 12 of the bag1 by an adhesive and sealing compound 40. The connection is restrictedto the radially inner region of the disc 16 and the end face 12 and islimited on the outside by a bead 41, which is provided in an annularmanner concentrically to the disc opening and to the disc circumferenceon that end face of the disc 16 which faces the bag 1. Outside theannular bead 41, the disc 16 and the bag end face 12 are not connectedand are generally removed from one another slightly. The disc 16 istherefore able to tilt freely within a certain angular range relative tothe bag end face 12, the bead 41 being pressed more on one side and lesson the other side into the bag. Any inclination of the bag, as indicatedin FIG. 2, is therefore unable to have an effect on the position of thedisc 16 and on the sealing effect of the O-ring 15.

In the embodiment according to FIG. 4, the end face 12 of the bag 1 isconnected to the disc 16 of the sealing ring 13 essentially over thefull area by means of the adhesive compound 40, so that the disc 16, asindicated in the drawing, participates in any deformation of the bagcaused by inclination. However, this cannot lead to a lack of tightness,since the sealing element of the sealing ring 13 is formed by a centricprojection 45 having a spherical surface 46. The projection surrounds anopening 47, through which the plait 7, which forms the bag opening 8,projects. The spherical surface 46 forms the sealing surface on the bagside.

The mating sealing surface is formed by the edge 43, which is obtainedon the base 4 of the cartridge at the transition between the end face 11and its delivery opening 9. The edge 43 lies in the plane of the face 11and is circular. Its diameter is less than the outside diameter of thespherical projection 45. Therefore the edge 43 is able to provide a sealon the spherical sealing surface 46 along a closed encircling sealingline. A similar effect is achieved if the sealing surface is conical,provided its cone angle is more obtuse than that of a wall 44, if needbe of conical design, of the discharge opening 9.

The diameter of curvature of the spherical sealing surface 46 isconsiderably larger than the diameter of the sealing edge 43, so thatwedging of the spherical sealing surface in the edge 43 or the wall 44of the opening 9 cannot take place. The tangent at a contact pointbetween the spherical sealing surface 46 and the sealing edge 43 formswith the axis of the sealing edge 43 an angle which is expedientlygreater than 30° and furthermore expediently greater than 40°. However,the angle should be less than 60°, so that the projection 45 is centredautomatically relative to the edge 43. The same correspondingly appliesto a conical form of the projection 45.

This embodiment not only has the advantage of insensitivity toinclination of the sealing ring but also leads to especially reliablesealing, since the sealing pressure against the edge 43 is high and anycontaminants are squeezed out of the way.

In the embodiment according to FIGS. 5 and 6, the bag 1 is provided witha disc 20 on the discharge side, and this disc 20 carries an O-ring 22at its centre opening 21, which lets the bag end through. The outsidediameter of the disc 20 is slightly larger than the inside diameter ofthe cartridge wall 3. When the bag with the disc 20 is advanced in thedirection of the arrow, the elastically resilient disc is thereforedeformed in such a way that its outer rim is supported obliquely againstthe cartridge wall 3. This inclined position of the rim 23 relative tothe cartridge wall 3 is retained even when the disc reaches its endposition (FIG. 6). If the piston pressure now ceases, the disc 20 cannotreadily give way, since there is a self-locking friction ratio betweenits rim 23 and the inner surface of the cartridge wall 3. The seal 22therefore remains pressed against the end face 11 under the elasticforce of the disc 20. This applies in principle even if the self-lockingeffect at the rim 23 of the disc is dispensed with and merely a frictiongrip of some kind or another is provided between the rim 23 and thecartridge wall 3, the resistance of which friction grip is at least inthe same order of magnitude as the force acting during the breathing onthe end face of the bag as a result of the back pressure.

FIG. 7 shows the arrangement having a brake element attached to the rearend of the tubular bag. Put onto the tubular bag 1 at its end is a disc30, which, in the centre, contains an opening for receiving the closingcord 31 of the bag. Its circumference interacts in a frictional mannerwith the inner surface of the cartridge 2. When the tubular bag ispushed into the cartridge in the direction of the arrow from its endremote from the base, the push-in force is transmitted to the bag viathe disc 30. The friction force at the circumference of the disc 30therefore does not have an effect on the internal pressure of the bag 1.If the cartridge with bag contained therein is stored outside thedelivery device and is placed in the vertical position with the end 6downwards, the friction force at the circumference of the disc 30absorbs the weight of the filled bag 1 and holds it in the existingposition.

The circumference of the disc 30 may be provided with features whichkeep the friction force within a desired range even in the presence ofcertain dimensional tolerances of the disc 30 and the cartridge 2; forexample it may be provided with a friction-increasing elastomeric ring.

An embodiment which, although it sets a friction force of desiredmagnitude against the reverse movement of the bag, offers only lowerresistance to the pushing of the bag into the cartridge from its rearend will be preferred in many cases. Suitable for this purpose are, forexample, embodiments in which the plane 33 in which the line of contactbetween the circumference of the disc 30, serving as brake element, andthe inner surface of the cartridge 2 lies is offset rearwards relativeto the main plane 34 of the disc. During axial movement of the disc, thefriction produces a bending moment at the circumference of the disc, andthis bending moment pushes the contact region radially inwards whilereducing friction during movement directed into the cartridge andradially outwards while correspondingly increasing friction in the caseof the reverse direction of movement.

The circumference of the disc 30, which circumference bears against theinner wall of the cartridge 2, need not be continuous; on the contrary,it may be discontinuous, so that a plurality of flexible arms areformed, the ends of which bear in a flexible manner against thecartridge wall and are connected to one another merely in the centralregion.

The axial offset between the contact plane 33 and the main plane 34 ofthe disc 30 or its arms need not be predetermined by the original formof the disc 30; on the contrary, the part may also be of flat design andmay not assume the form curved rearwards on the outside until it iselastically deformed when being pushed into the cartridge.

What is claimed is:
 1. Arrangement for squeezing out a free-flowingsubstance, comprising an elongated tubular bag (1), which contains thesubstance and has, at least at one end, an opening (8) surrounded by ashoulder (12) of the tubular bag (1) and by a sealing ring (13)connected to the shoulder (12) and having or forming at least onesealing element (15, 22, 45), and a squeezing-out device (2, 5), whichhas a cylinder space (10), which accommodates the tubular bag, receivesa pressure piston (5) at one end and contains a discharge opening (9) atthe other end, the discharge opening (9) interacting with the bagopening (8) and being surrounded by an end face (11) lying opposite theshoulder (12) of the tubular bag (1) and the sealing ring (13),characterized in that the sealing element (15, 22, 45) of the sealingring interacts solely with the end face (11) surrounding the dischargeopening (9), namely with that edge of the discharge opening which isformed by this end face (11).
 2. Arrangement according to claim 1,characterized in that the sealing ring (13) is connected to the bag (1)in such a way as to be movable in an angular manner in relation to thebag axis (42).
 3. Arrangement according to claim 2, characterized inthat the sealing ring (15) is connected to a disc (16) or is designed asa disc, which is adhesively bonded to the bag end face (12) inside anannular bead (41), which faces the bag end face (12) and whose diameteris substantially smaller than that of the bag (1).
 4. Arrangementaccording to claim 1, characterized in that the sealing surface (46) ofthe sealing element (45) is of spherical or conical design, and theangle (42) between the tangent applied at the contact point and thecentre line (42) is substantially larger than the angle between thedirection of the wall (44) of the discharge opening (9) and the centreline (48).
 5. Arrangement for squeezing out a free-flowing substance,comprising an elongated tubular bag (1), which contains the substanceand has, at least at one end, an opening (8) surrounded by an end face(12) of the tubular bag (1) and by a sealing ring (13) connected to theend face (12) and having or forming at least one sealing element (45),and a squeezing-out device (2, 5), which has a cylinder space (10),which accommodates the tubular bag, receives a pressure piston (5) atone end and contains a discharge opening (9) at the other end, thedischarge opening (9) interacting with the bag opening (8) and having asealing surface (43) interacting with the surface of the sealing ring(13), characterized in that the sealing-ring surface and the sealingsurface (43) are spherical.
 6. Arrangement according to claim 1,characterized in that the angle (48) between the tangent at the contactpoint of the sealing surfaces (43, 46) and the centre line (42) isgreater than 30°.
 7. Arrangement according to claim 1, characterized inthat, to centre the bag opening (8) relative to the discharge opening(9), the outside diameter of the annular disc (14) is not much smallerthan that of the cylinder space (10).
 8. Arrangement according to claim1, characterized in that the circumferential surface (28) of the sealingring (13) has a height of at least 4 mm or 6% of the sealing-ringdiameter.
 9. Arrangement according to claim 1, characterized in that thesealing ring is provided with at least one retaining part arresting itin the sealing position.
 10. Arrangement according to claim 9,characterized in that the retaining part is designed as a clamp (23)interacting with the inner wall of the cylinder space.
 11. Arrangementaccording to claim 10, characterized in that the retaining part isdesigned as at least one suction holder (26) interacting with the endface (11).
 12. Arrangement according to claim 1, characterized in that abrake element (30) interacting in a frictional manner with the wall (3)of the cylinder space (10) at least in the direction which leads the bag(1) out of the cylinder space (10) is provided at that end of the bag(1) which is opposite the end containing the opening (8). 13.Arrangement according to claim 12, characterized in that the brakeelement (30) comprises a disc or a ring, via which the pressure piston(5) acts on the tubular bag.
 14. Arrangement according to claim 12,characterized in that the circumference, if need be discontinuous, ofthe brake element (30) has a diameter which is larger than the insidediameter of the cylinder space (10).
 15. Arrangement according to claim12, characterized in that the plane (33) of contact between the brakeelement (30) and the wall (3) of the cylinder space (10) is offset inthe direction away from the tubular bag (1) relative to that plane (34)of the region of the brake element which bears against the tubular bag(1).
 16. Arrangement for squeezing out a free-flowing substance,comprising an elongated tubular bag (1), which contains the substanceand has, at least at one end, an opening (8) surrounded by an end face(12) of the tubular bag (1) and by a sealing ring (13) connected to theend face (12) and having or forming at least one sealing element (45),and a squeezing-out device (2, 5), which has a cylinder space (10),which accommodates the tubular bag, receives a pressure piston (5) atone end and contains a discharge opening (9) interacting with the bagopening (8) and having a sealing surface (43) interacting with thesurface of the sealing ring (13), characterized in that the sealing-ringsurface or the sealing surface (43) is spherical.